The invention relates to herbicide compositions and their preparation and use, and in particular to methods and compositions relating to microemulsion-forming compositions that contain herbicide compound in acid form, to microemulsions and other herbicide compositions derived from the microemulsion-forming-compositions, and to the related methods of preparation and use.
Commercially available herbicide compositions include a very large variety of active herbicide compounds. Herbicide compositions can be prepared from a variety of different types of precursor compositions, and can be commercially available and used in a variety of different types of compositions, including compositions referred to as wettable powders, water dispersible granules, granules, aqueous solutions, water soluble powders, emulsifiable concentrates, oil-based flowables, concentrated emulsions, suspo-emulsions, emulsions, suspensions, suspension concentrates, mixtures, dispersions, and microemulsions, as well as others. Any of these different types of compositions may have different advantages or disadvantages depending on what type of active ingredients the herbicide includes.
Examples of just a few available active herbicide compounds include those of the general class known as phenoxy herbicides, e.g., 2,4-dichlorophenoxyacetic acid (known as 2,4-D), MCPA acid, MCPP acid; those of the general class known as pyridine herbicides, (e.g., triclopyr, fluoroxypyr); those of the general class of benzoic acid herbicides, (e.g., dicamba acid); those of the general class of aryloxy phenoxy propionic acid herbicides, (e.g., fluazifop acid and quizolofop acid); water-insoluble diphenyl ether type herbicides (e.g., oxyfluorfen or acifluorfen); glyphosate compounds (e.g., in the IPA salt form); imidizole herbicide compounds (e.g., imazapyr or imazaquin); as well as others.
Active herbicide ingredients such as these and others can be prepared from and used in the form of solid and liquid compositions including, as mentioned above, different forms of emulsions, suspensions, suspension concentrates, mixtures, dispersions, and microemulsions, etc. With regard to the liquid forms, the active ingredient (herbicide compound) is generally suspended or dissolved in a liquid, with the active herbicide compound taking the chemical form of a salt or ester, depending on which form is either soluble or suspendable in such a liquid composition. Most herbicide compositions are prepared from an ester or salt form of a herbicide compound, or are prepared using a step to convert an acid form of a herbicide compound to a salt or an ester to be either miscible in water or emulsifiable in water for application, often with the assistance of organic solvent.
With microemulsion compositions in particular, earlier microemulsion work typically included the use of herbicide compounds in forms other than their acid forms, e.g., ester or salt forms, because the salt or ester forms were considered to be most easily dispersed or suspended in a microemulsion. Typical microemulsions also incorporated organic solvents to effect suspension or dissolution of the herbicide compound.
New forms of effective herbicide compositions are always desirable, especially those that show advantages in processing, application, environmental profile (e.g., volatility), or efficacy. And there is always a desire to prepare herbicide compositions that reduce or eliminate organic solvents.
The invention relates to the use of herbicide compounds existing in their acid forms, dissolved in one or a combination of surfactants to form what is referred to herein as a microemulsion-forming-concentrate, or xe2x80x9cMFC.xe2x80x9d The MFCs and their derivatives can be useful as herbicide compositions. The MFCs are preferably relatively stable compositions that at a desired time can be mixed or diluted with water to form a microemulsion or other derivative for application to control plant growth either alone or in combination with other ingredients such as other herbicides or additives, such as acidifying agents.
The MFCs can generally be prepared by mixing a selected herbicide compound in acid form into a surfactant or a mixture of surfactants, with optional heating and agitation, and with optional organic solvent. Exemplary amounts of herbicide compound and surfactant can be in the range from about 10 to about 40 parts by weight herbicide compound in acid form, and about 60 to about 90 parts by weight surfactant. The MFC may include amounts of water and organic solvents, but preferred MFCs can be made with reduced, minimal, or no organic solvent, e.g., with no added organic solvent.
The MFCs can be directly applied as herbicide compositions, or, preferably, can be combined with water and optionally other ingredients such as another herbicide or an acidifying agent, and then applied to control plant growth. For example, depending, e.g., on the herbicide compound and other factors, from about 0.05 to about 7 parts by volume MFC may be diluted with about 93 to about 99.95 parts by volume water to form a microemulsion. Other ingredients such as acidifying agent or other herbicides may also be added.
If an acidifying agent is added to the MFC or the microemulsion, the acidifying agent can preferably be added in an amount such that the pH of the microemulsion is below the pKa of the herbicide compound of the microemulsion, so that herbicide compound will be present in acid form. The use of herbicide compounds in acid form has been found to be advantageous. For example, many herbicide compositions having active herbicide compounds in their acid form can be prepared efficiently, can show particularly good efficacy, and can be unaffected or less affected by hard water.
An aspect of the invention relates to a microemulsion-forming-concentrate comprising herbicide compound in acid form and surfactant, wherein the concentrate can be combined with water to form a microemulsion. Preferred microemulsion-forming-concentrates can consist of or consist essentially of herbicide compound in acid form and surfactant, optionally including such additives as anticorrosion agents, antifoam agents, water, and organic solvent.
Another aspect of the invention relates to a microemulsion-forming-concentrate consisting of herbicide compound in acid form and surfactant, with optional acidifying agent or additives as discussed herein, and with no added organic solvent or added water, wherein the microemulsion-forming-concentrate can be combined with water to form a microemulsion.
Another aspect of the invention relates to a microemulsion comprising herbicide compound in acid form, surfactant, and water.
Another aspect of the invention relates to a microemulsion comprising a microemulsion-forming-concentrate comprising herbicide compound in acid form and surfactant, combined with water to form a microemulsion.
Another aspect of the invention relates to a method of applying a herbicide composition. The method comprises: preparing a herbicide composition comprising a microemulsion comprising herbicide compound in acid form and surfactant; and applying the herbicide composition comprising the herbicide compound in acid form to a plant or field to control plant growth.
Another aspect of the invention relates to a method of applying a herbicide. The method comprises preparing a microemulsion-forming-concentrate comprising herbicide compound in acid form and surfactant; preparing a microemulsion from the concentrate by diluting the microemulsion with an aqueous solution, the microemulsion comprising herbicide compound in acid form; and applying the herbicide composition to a plant to control plant growth while the herbicide compound is in acid form.
Yet another aspect of the invention relates to a method of preparing a microemulsion-forming-concentrate. The method comprises combining herbicide compound in acid form with surfactant, with optional heat and optional agitation, to produce a concentrate that can be combined with water to form a microemulsion.
Still another aspect of the invention relates to a method of preparing a microemulsion. The method comprises preparing a microemulsion-forming-concentrate by a method comprising combining herbicide compound in acid form with surfactant to produce a concentrate that can be combined with water to form a microemulsion; and combining the microemulsion-forming-concentrate with water to form a microemulsion.
The invention relates to herbicide compositions in the form of microemulsion-forming-concentrates and derivatives thereof. The term xe2x80x9cherbicide compositionxe2x80x9d refers to a composition that includes a herbicide compound. Herbicide compositions include microemulsion-forming-concentrates and derivatives thereof such as microemulsions or herbicide application compositions, each of which is discussed in more detail below. The term xe2x80x9cmicroemulsionxe2x80x9d (xe2x80x9cMExe2x80x9d) means a solution that contains an oil phase and water, wherein the oil phase is finely dispersed such that light passes through the microemulsion and the microemulsion may be opaque or clear in appearance. Microemulsions are a known type of composition, and are sometimes considered either as micellar solutions containing inverted micelles (hydrophobic tails oriented toward the external oil phase and hydrophilic heads in the inner core) with water solubilized in the inner core, or as emulsions containing tiny droplets of water surrounded by an interfacial film. See, e.g., Surfactants and Interfacial Phenomena, Milton J. Rosen, Page 239and240, John Wiley and Sons (1978).
Microemulsion-forming-concentrates or xe2x80x9cMFCsxe2x80x9d of the invention include a herbicide compound in acid form dissolved in surfactant, optionally water, optionally may but preferably do not include added organic solvent, and can be diluted with water to form a microemulsion. MFCs can typically be translucent, opaque, or even clear solutions.
Different classes of herbicide compounds and different specific herbicide compounds within these classes can be used to produce MFCs according to the invention. A large variety of such herbicide compounds are well known and commercially available, and one of skill will be able to identify useful combinations of herbicide compound and surfactant useful to prepare herbicide compositions according to the invention, based on the present description. Suitable herbicide compounds can include herbicide compounds that act as a pre-emergent or post-emergent systemic herbicide, and that can exist in an acid form that can be dissolved in surfactant, optionally with the use of water or organic solvent, to form an MFC. Compositions and methods of this invention are particularly beneficial when using herbicides having post-emergent activity, i.e., systemic herbicidal activity toward established plants, due to the improvements in post-emergent, systemic activity available with these compositions and methods. While wishing not to be bound by theory, it is believed that the use of a herbicide compound in acid form, especially applied directly to a plant, and especially in a herbicide composition having an acidic and a relatively low pH (e.g., below 7, 6, or 5, or below the pKa of a herbicide compound, or lower) can effect improvements in plant control by one or both of the following mechanisms. First, a charge-neutral molecule (such as an acid) can have an easier time penetrating a cuticle on a plant compared to a charged molecule (e.g., salt). Secondly, when the herbicide compound in acid form is applied with a herbicide composition containing an acidifying agent and at a low pH, the acidifying agent and low pH can have a damaging effect on a plant""s surface, thereby allowing more herbicide compound to penetrate the plant surface. Also, the acid form of a herbicide compound, due to its uncharged state, can be advantageously less affected or unaffected by hard water, e.g., less susceptible to de-activation by hard water.
Herbicide compounds may typically be available in ester or salt forms, and many herbicide compositions are conventionally sold commercially to contain herbicide compounds in either a salt or ester form, which are often considered to be relatively soluble, dispersible, or emulsifiable in water, as opposed to acid forms which are often less soluble in water. Acid forms of herbicides are used according to the invention.
xe2x80x9cHerbicide compound in acid form,xe2x80x9d herein refers to a herbicide compound that exists in a form of the compound that is considered to be the xe2x80x9cacidxe2x80x9d form of the compound, as opposed to a different chemical form of the same compound such as a salt or an ester form. Many herbicide compounds are capable of existing in discernible, understood, chemically-different forms, including, e.g., an acid form, an ester form, or a salt form. The term xe2x80x9cherbicide compound in acid formxe2x80x9d includes herbicide compounds of these types, when the compound is in the acid as opposed to an ester or a salt or other non-acid form.
One way of identifying a herbicide compound in acid form is to reference a pKa of a herbicide compound. The pKa of a herbicide compound is understood to refer to the negative logarithm (base 10) of the equilibrium constant K for the reaction of the herbicide compound between its acid form and its neutral form. Methods of determining the pKa for a herbicide compound will be readily understood by the skilled artisan. Exemplary herbicide compounds that are capable of existing in acid form can have a pKa below about 6, or below about 5 or 4. Some herbicide compounds include more than one acidic hydrogen and therefore have more than a single pKa value. According to the invention, the relevant and referred to pKa is the pKa of a herbicide compound that relates to the change of the compound between the compound considered to be the deprotonated xe2x80x9cacidxe2x80x9d form of the compound, and what is considered to be the protonated (neutral) form of the xe2x80x9cacidxe2x80x9d form. The protonated acid form predominates at pH below the pKa, and the deprotonated form predominates at pH above the pKa. Examples of exemplary pKa values for certain herbicide compounds are included in the Table 1.
Some examples of useful herbicide compounds that can be used in their acid forms to produce MFCs in surfactant include the following, some or all of which are commercially available in their acid form (though presently not generally sold in that form as herbicide formulations). For herbicide compounds that are sold in a form other than the acid form, such as a salt or ester form, a skilled chemist will understand how to convert the non-acid to an acid form for use as described herein.
The class of phenoxy herbicides generally includes herbicides derived from chlorinated phenols, and includes herbicide compounds that can exist in an acid form. Examples include the well known herbicides 2,4-dichlorophenoxyacetic acid (known as 2,4-D), 4-methyl-4-chlorophenoxyacetic acid (MCPA Acid), and 2(-2-methyl-4-chlorophenoxy)propionic acid (MCPP acid), as well as others.
Pyridine herbicides are herbicides derived from a pyridine ring-containing compound, and includes herbicide compounds that can exist in an acid form. Examples include 3,5,6-trichloro-2-pyridyloxyacetic acid (triclopyr acid) and fluroxypyr (4-amino-3,5-dichloro-6-fluoro-2-pyridyloxyacetic acid), as well as others.
Benzoic acid herbicide compounds include or are derived from benzoic acid compounds. This class of herbicide compounds includes herbicide compounds that can exist in an acid form. A single example is dicamba acid (3,6-dichloro-O-anisic acid), but others could also be used according to the invention.
Aryloxy phenoxy propionic acid herbicide compounds (also referred to sometimes as xe2x80x9coxyphenoxyxe2x80x9d herbicides), are another class of herbicides that can exist in an acid form. Examples of specific compounds include fluazifop acid and quizolofop acid, as well as others.
The herbicide compound in acid form is dissolved in surfactant (and optionally water and organic acid) to form an MFC that contains surfactant and dissolved herbicide compound in acid form.
A very large variety of surfactants are known and commercially available, including such different classes as cationic surfactants, anionic surfactants, non-ionic surfactants, ionic surfactants, and amphoteric surfactants. According to the invention, the surfactant can be any surfactant or combination of two or more surfactants useful to dissolve the herbicide compound in its acid form to produce a microemulsion-forming-concentrate.
Examples of some preferred surfactants include cationic, non-ionic, and anionic surfactants. Of these, some even more specific types of preferred surfactants include non-ionic linear or branched alcohol ethoxylate surfactants, anionic phosphoric acid ester surfactants (sometimes referred to as xe2x80x9cphosphate esterxe2x80x9d surfactants), and cationic ethoxylated tallow amine surfactants. Examples of surfactants and identification of their intermediate and general classifications are as follows:
An anionic surfactant is a surface-active molecule in which an active portion of a lipophilic portion of the molecule forms a negative ion (i.e., anion) when placed in aqueous solution. Exemplary anionic surfactants include phosphoric acid ester surfactants (sometimes referred to as xe2x80x9cphosphate esterxe2x80x9d surfactants), sodium alkyl naphthalene sulfonate surfactants, and ethoxylated tristyrylphenol phosphate salts.
Exemplary sodium alkyl naphthalene sulfonate surfactants include sodium butyl naphthalene sulfonate, sodium di-n-butyl naphthalene sulfonate, sodium diisopropyl naphthalene sulfonate, sodium dimethyl naphthalene sulfonate, and mixtures thereof. Sodium butyl naphthalene sulfonate is commercially available, for example, under the trade name xe2x80x9cMORWET Bxe2x80x9d from Witco/Crompton, Greenwich, Conn. Sodium di-n-butyl naphthalene sulfonate is commercially available, for example, under the trade name xe2x80x9cMORWET DBxe2x80x9d from Witco/Crompton, Greenwich, Conn. Sodium diisopropyl naphthalene sulfonate is commercially available, for example, under the trade name xe2x80x9cMORWET IPxe2x80x9d from Witco/Crompton, Greenwich, Conn. Sodium dimethyl naphthalene sulfonate surfactant is commercially available, for example, under the trade name xe2x80x9cSELLOGEN HRxe2x80x9d from Henkle Corp., Cincinnati, Ohio.
An exemplary ethoxylated tristyrylphenol phosphate potassium salt surfactant is commercially available, for example, under the trade name xe2x80x9cSOPROPHOR FLKxe2x80x9d from Rhodia, Cranbury, N.J.
A nonionic surfactant is a surface-active molecule that does not contain ionizable polar end groups but does contain hydrophilic and lipophilic portions. Exemplary nonionic surfactants include polyoxyethylene alkylether or alkenylether surfactants. Nonionic surfactant used to prepare a suspension concentrate as described herein may include long or short chain alcohol ethoxylate surfactant. The alcohol ethoxylate surfactant may be branched or linear.
An example of a useful nonionic polyoxyalkylene surfactant includes alcohol ethoxylate having the general formula:
Rxe2x80x94Oxe2x80x94((CH2)xO)yxe2x80x94H
wherein R may be xe2x80x9clongxe2x80x9d or xe2x80x9cshortxe2x80x9d chain and xe2x80x9cbranchedxe2x80x9d or xe2x80x9clinearxe2x80x9d alkyl. R preferably can be a xe2x80x9cshort chainxe2x80x9d branched or linear alcohol, meaning that it can have from about 3 to 23 or fewer carbon atoms. With respect to the oxyalkylene, x can preferably be in the range from about 2 to 5, preferably from about 2 to 4 (e.g., 2 or 3, for a polyoxyethylene or polyoxypropylene, respectively) and y can preferably be in the in the range from 5 to 25.
Examples of useful short chain nonionic polyoxyalkylenes include linear alcohol polyoxyethylenes having the general formula:
CH3(C2H4)mO(C2H4O)nH
wherein CH3(C2H4)m is a short chain linear alkyl having from about 3 to 23 or fewer carbon atoms (i.e., m can be in the range from about 1 to 11 carbon atoms), and n is in the range from about 5 to 25.
Another example is short chain nonionic polyoxypropylenes having the general formula:
xe2x80x83CH3(C2H4)mO(C3H6O)nH,
wherein CH3(C2H4)m is a short chain linear alkyl having from about 3 to 23 or fewer carbon atoms (i.e., m can be in the range from about 1 to 11 carbon atoms), and n can preferably be in the range from about 5 to 25.
Exemplary short chain linear alcohol ethoxylate surfactant are commercially available, for example, under the trade names xe2x80x9cSURFONIC L12-6xe2x80x9d from Huntsman, Austin, Tex., xe2x80x9cSURFONIC L24-7xe2x80x9d from Huntsman, Austin, Tex., xe2x80x9cTERGITOL 15-S-7xe2x80x9d, xe2x80x9cTERGITOL 24-L-60xe2x80x9d, xe2x80x9cALPHONIC 1012-60xe2x80x9d, xe2x80x9cALPOHONIC 1414-60xe2x80x9d, xe2x80x9cBIOSOFT ET 630, xe2x80x9d from Stepan Company, Chicago, Ill., and xe2x80x9cGENOPAL 24-L-60.xe2x80x9d
Other exemplary surfactants include polyethylene glycol, fatty acid ethoxylates, phosphate esters, octyl phenol ethoxylates, and nonyl phenol ethoxylates.
Useful polyethylene glycol surfactants are commercially available, for example, under the trade names xe2x80x9cADEKA PEGxe2x80x9d from Asahi Denka Kogyo, Tokyo, Japan.
Useful fatty acid ethoxylate surfactants are commercially available, for example, under the trade names xe2x80x9cNINEX MT-610xe2x80x9d, xe2x80x9cNINEX MT-615xe2x80x9d, and xe2x80x9cNINEX MT-630xe2x80x9d from Stepan, Northfield, Ill.
Useful phosphate ester surfactants are commercially available, for example, under the trade names xe2x80x9cSTEPFAC 8180xe2x80x9d, xe2x80x9cSTEPFAC 8181xe2x80x9d, and xe2x80x9cSTEPFAC 8182xe2x80x9d from Stepan.
Useful octyl phenol ethoxylate surfactants are commercially available, for example, under the trade name xe2x80x9cMAKON OP-9xe2x80x9d from Stepan, Northfield, Ill.
Useful nonyl phenol ethoxylate surfactants are commercially available, for example, under the trade names xe2x80x9cMAKON 4xe2x80x9d, xe2x80x9cMAKON 6xe2x80x9d, xe2x80x9cMAKON 8xe2x80x9d, xe2x80x9cMAKON 10xe2x80x9d, xe2x80x9cMAKON 12xe2x80x9d, and xe2x80x9cMAKON 14xe2x80x9d from Stepan, Northfield, Ill.
A cationic surfactant is a surface-active molecule in which an active portion of a lipophilic portion of the molecule forms a positive ion (i.e., cation) when placed in aqueous solution. In one embodiment, exemplary cationic surfactant includes ethoxylated tallow amine.
Generally speaking, the amounts of surfactant and herbicide compound in the MFC can be any useful amounts, meaning that the amounts are sufficient to produce a useful herbicide composition or a useful herbicide composition precursor, based on the amount of herbicide dissolved in the surfactant. Amounts of either organic solvent or water may also be used to produce an MFC, but it is preferred that only small amounts or organic solvent and more preferably no organic solvent be added to the MFC. Useful relative amounts of herbicide and surfactant will vary for different herbicide compounds and different surfactants, as well as the optional presence of organic solvent or water. Exemplary MFCs can include from about 10 to about 40 parts by weight, e.g., from about 20 to about 35 parts by weight herbicide compound in acid form, and from about 60 to about 90, e.g., from about 65 to about 80 parts by weight surfactant.
The MFC may include water and organic solvents to facilitate dissolution of the herbicide compound. An exemplary amount of organic solvent may be below about 20 percent by weight e.g., below about 10 percent by weight, and an exemplary amount of water may also be below about 20 percent by weight, e.g., below about 10 percent by weight, for a total amount of water and organic solvent up to about 40 percent by weight. Preferred MFCs can be made with minimal or no amounts of water or organic solvents. Generally, small amounts or no amount of organic solvent or water can be preferred, such that the MFC contains substantially no organic solvent or water. Compositions described herein may include some amounts of organic solvent or water present due to processing history of ingredients used to produce the MFC, such as the preparation of a surfactant or herbicide compound using an organic solvent or water, but that amount of organic solvent or water will normally be less than 5 weight percent or less than 1 weight percent of the total MFC composition, e.g., less than 0.5 or 0.1 weight percent of the total weight of the MFC composition. xe2x80x9cSubstantially no organic solventxe2x80x9d means that a composition includes no added organic solvent, but may include residual organic solvent as noted. xe2x80x9cSubstantially no waterxe2x80x9d means that a composition includes no added water, but may include residual water as noted.
The MFC is preferably stable in the form of a microemulsion-forming-concentrate, for a useful period, meaning that the composition does not settle or otherwise transform out of the MFC form, and maintains the form of an MFC for a useful amount of time, after which the MFC can be diluted with water to form a microemulsion. Useful periods of stability can depend on the timing of dilution and application of the MFC following preparation of the MFC, which time period can vary greatly, e.g., based on convenience, preference, or other factors. If an MFC or derivative can be applied (typically following dilution) in a short or very short period of time after preparation of the MFC, any amount of longer-term stability is not required. Exemplary MFCs of the invention have been found to be stable at approximately room temperature and in substantially undisturbed and un-agitated environments for periods in excess of 6 or 12 months. Longer or shorter periods would also be useful.
The MFC can be applied directly to a field or plant to control undesired plant growth, or can be diluted with water to form a microemulsion, which, optionally with other ingredients as described below, can be applied to a field or plant as a xe2x80x9cherbicide application compositionxe2x80x9d to control undesired plant growth. xe2x80x9cHerbicide application compositionxe2x80x9d refers to a herbicide composition having a concentration of herbicide compound that would normally be applied to a field or plant to control undesired plant growth, as opposed, for example, to compositions having higher concentrations of herbicide compound that sometimes occur in preparation, storage, shipping, or sale of a herbicide composition. It is noted that any of the herbicide compositions described herein, such as the MFC, may be capable of controlling plant growth, e.g., if applied directly to a plant. Yet it is typical for reasons of efficiency, cost, convenience, techniques presently used in applying herbicide compositions, and environmental considerations, to use a relatively diluted form of herbicide composition to conveniently apply a specific and known amount of herbicide compound per acre or per other unit of application. By way of example, herbicide application compositions include any herbicide composition having such a specific concentration of herbicide compound for application, e.g., to a field, and specifically include microemulsions prepared directly by diluting an MFC with water, and microemulsions or other solutions prepared by diluting an MFC with water and adding one or more other optional ingredients, as will be described in more detail below.
Relative amounts of MFC and water used to prepare a microemulsion can be any amounts that produce a useful microemulsion, and can depend on factors such as the composition of the MFC (e.g., the type and concentration of the herbicide compound), the intended application (including the plant to be controlled or the crop to be protected), the mode of application (e.g., field or aerial spraying or application from a hand-held spray applicator, or other technique), etc.
Although amounts outside of the following ranges can also be useful, and exact ratios can depend significantly on the identity of herbicide compound used, exemplary MFCs can be combined with water to form a microemulsion by mixing about 0.05 to about 7 parts by volume MFC with from about 93 to about 99.95 parts by volume water (e.g., 2 ml MFC to 98 ml water, 1 quart MFC to 12 gallons water, 12 oz. MFC to 20 gallons water, 0.065 parts MFC to 99.935 parts water, or equivalent amounts of each). The actual amount of MFC to water can vary depending on the crop, weed species, the amount of spray volume as chosen by the applicator, the desired strength of the application composition, or whether other ingredients are included or added. This composition may be applied as a herbicide application composition, optionally additionally including other ingredients such as a desired amount of acidifying agent or one or more other herbicide.
Additional ingredients can be included in the MFC or herbicide composition for purposes of stability, pH adjustment, anti-foaming, or to facilitate application or to increase efficacy. These other ingredients may be added to the MFC or herbicide application composition at any time and in any order, as desired and convenient. Exemplary additional ingredients include antifoaming agents, acidifying agents, anticorrosion agents, etc.
Antifoaming agents are well understood in the chemical and herbicide arts, and a variety of useful examples are commercially available. As is known, antifoam agents are substances, such as silicones, organic phosphates, and alcohols, which inhibit the formation of bubbles in a liquid during its agitation by reducing its surface tension. One specific example of a commercially available antifoam agent is SAG 10 (a 10% silicone in water antifoam), commercially available from Witco OSI. The amount of antifoaming agent used in an MFC or in a microemulsion will also be apparent to the skilled artisan, with typical amounts being less than 1 percent by weight, e.g., less than 0.5 percent.
A preferred embodiment of a herbicide application composition can further include an acidifying agent, particularly an acidifying agent that improves the efficacy of the herbicide composition. A variety of different acidifying agents can be useful with the herbicide compositions of the invention, e.g., to improve efficacy of a herbicide composition. Examples of a certain type of acidifying agent are described in U.S. Pat. Nos. 4,445,925, 4,994,101, 5,288,692, the disclosures of which are incorporated herein by reference. Other exemplary acidifying agents are known, and still others are described in Assignee""s copending U.S. Patent Application entitled xe2x80x9cHerbicide Composition Comprising Herbicide Compound in Acid Form and Acidifying Agent,xe2x80x9d having Attorney""s Docket Number UAP0006/US/2, and Ser. No. ______, filed on even date herewith, and incorporated herein by reference. See also Assignee""s copending U.S. Patent Application entitled xe2x80x9cHerbicide Compositions Comprising Suspension Concentrate with Glyphosate Acid, Methods of Preparation, and Methods of Use,xe2x80x9d having Attorney""s Docket Number UAP0007/US/2, and Ser. number ______, filed on even date herewith, and incorporated herein by reference.
The particular acidifying agent chosen and the amount used can be based on factors such as the intended application (including the identity of the undesirable plant growth, and the desired plant growth), the method of application, the herbicide compound chosen, physical and chemical properties of the herbicide application composition, and other factors. The acidifying agent may be any of a variety of suitable organic and inorganic acids, of any useful strength or concentration (e.g., concentrated or diluted), that can be added to an MFC or a microemulsion, etc., preferably without causing substantial or undue negative effects such as reaction with another ingredient such as the herbicide compound, precipitation, etc.
Non-limiting examples of specifically useful acidifying agents include acids such as sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid (e.g., xe2x80x9cglacialxe2x80x9d acidic acid), perchloric acid, polyphosphoric acid, acidic adducts such as the sulfuric acid adducts described in U.S. Pat. No. 5,288,692 (Young), especially the adduct of sulfuric acid and urea, and any other acidifying agent that can be used to affect the pH of a herbicide composition. It will be understood that such acidifying agents can be used alone or in combination, and can be included in a herbicide composition in a concentrated or a diluted form.
One useful type of acidifying agent includes adducts of sulfuric acid and an xe2x80x9camidexe2x80x9d according to the formula: 
wherein X is chalcogen, and each of R1, R2, and R3 is independently selected from hydrogen and organic radicals. As used herein, xe2x80x9camidexe2x80x9d encompasses all compounds of formula (1) regardless of the chalcogen. The molar ratio of amide to acid is usually in the range of about xc2xc to less than 2 so that at least some of the acid is present as the monoamide-acid adduct.
When R1, R2, and R3 are organic radicals, they may be cyclic or acyclic, straight, or branched chained, and can contain one or more heteroatoms such as sulfur, nitrogen, oxygen, phosphorus and the like. Further, R1, R2, and R3 can contain one or more substituents such as thiol, hydroxy, nitro, amino, nitrile, amide, ester and halogen groups and others. Such organic radicals may contain aryl groups such as aralkyl and alkaryl groups. Certain preferred organic radicals can be free of olefinic or alkynyl unsaturation and can generally have up to about 20, preferably up to about 10 carbon atoms. Particularly preferred amides include urea, thiourea, formamide, dimethylformamide, biuret, triuret, thioformamide, and combinations of these.
The chalcogens are elements of Periodic Group VI-B and include oxygen, sulfur, selenium, tellurium, and polonium. Oxygen and sulfur can be preferred due to low cost, availability, low toxicity, and chemical activity, and oxygen is the most preferred.
An example of a specific adduct of formula (1) is the sulfuric acid/urea adduct: 
Other types of useful acidifying agents, as stated, include sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid (e.g., xe2x80x9cglacialxe2x80x9d acidic acid), perchloric acid, polyphosphoric acid, other adducts, etc. Various such acids are commercially available in different forms and concentrations, including solids, liquid solutions, concentrated liquid solutions, etc., or can be prepared by one of ordinary skill. Any such form of acidifying agent may be useful to reduce the pH of a herbicide composition, preferably without causing any undue negative effect on the herbicide composition. Useful forms of these types of acidifying agents can include solid forms, liquid forms (aqueous forms), and concentrated liquid forms. The chosen form of an acidifying agent may be based on factors such as commercial availability, convenience, and the overall desired properties of the herbicide composition, its different ingredients (e.g., the herbicide compound), and its desired method of preparation and use.
The particular amount of acidifying agent added to an MFC, herbicide application composition, or other herbicide composition, can be selected depending on factors such as the particular herbicide composition and chemistry of the herbicide composition, including the amounts and chemistries of surfactant and herbicide compound; the amount and identity of any solvent; whether water is included and in what amount; the type of acidifying agent and its chemistry and strength (concentration); and based on the desired pH of the herbicide composition and the relevant pKa of the herbicide compound. As stated, preferred amounts of any particular acidifying agent can be capable of improving the efficacy of the herbicide composition, and particularly preferred amounts will be sufficient to produce an application composition having a pH below the relevant pKa of the herbicide compound.
Examples of useful amounts of acidifying agents will be quite varied, considering the above factors. Relatively strong concentrations of liquid (aqueous) acidifying agent solutions such as 93% liquid sulfuric acid, 72% phosphoric acid, 85% polyphosphoric acid, 90% nitric acid, 99% glacial acetic acid, etc., can be added directly or can be first diluted and then added to a herbicide composition in an amount to bring the pH to below about 7, e.g., below about 5 or 6, preferably below the pKa of the herbicide compound. In terms of volume percent, preferred amounts are highly dependent on the identity of the acidifying agent and the herbicide composition and its pKa. Very generally speaking, useful relative amounts of acidifying agent to microemulsion can be below about 5 or 10 volume percent, e.g., in the range from about 0.01 to about 4 percent by volume acid based on the total volume of herbicide application composition and acidifying agent.
The herbicide compositions of the invention can be used for immediate and long-term, pre-and post-emergent control of a large variety of different forms of vegetation, particularly upon appropriate selection of the herbicide compound.
As an example, the MFC could be applied directly for controlling the growth of a plant, although this may include an unnecessarily potent concentration of the herbicide compound, and it can be difficult to uniformly apply a small amount of concentrated herbicide to a large area without dilution. An MFC would instead more likely be a product sold as a herbicide concentrate product, which would be a composition that includes a relatively high concentration of a herbicide compound as manufactured or packaged for sale, and which may be diluted prior to use to form a herbicide application composition, especially a microemulsion.
The MFC could be purchased by distributors or suppliers, or directly by consumers, either one of which could add water and other optional ingredients such as an acidifying agent or another type of herbicide or herbicide compound to the MFC. The additives could, for example, be added and mixed in a tank immediately prior to application.
In one embodiment of a distribution system, an MFC could be sold to farming product or nursery dealers, or the like, who could dilute the MFC with water and/or add other ingredients such as an acidifying agent. This could be particularly convenient if such a dealer normally kept on hand a stock of acidifying agent such as phosphoric acid or sulfuric acid, etc. The MFC or a microemulsion from the MFC, combined with an acidifying agent by the dealer, could be sold to an end consumer, who could use it as purchased or who could optionally further dilute the purchased composition or add other ingredients to the purchased composition such as an additional herbicide by tank mixing.
The herbicide compositions can be applied for immediate vegetation control by contact killing, by application of a herbicide application composition to plants. Herbicide application compositions can contain a useful amount of herbicide compound, based on factors of efficacy and safety, etc. Similarly, the amount of herbicide application composition applied to a plant or a field will be readily understood by those of skill, based, e.g., on desired efficacy and safety and environmental factors.
The particular amount of herbicide compound in any specific herbicide application composition will depend on factors as known and described above, and depending in particular on the identity of the specific herbicide compound. Advantageously, it has been found that certain preferred application compositions of the invention, especially those that include an acidifying agent, those that are applied with the herbicide compound in acid form, and in particular those that also have a pH that is below the pKa of the herbicide compound, can be applied at lower dosages (lower amounts of herbicide compound per plant or per acre) relative to other herbicide compositions containing the same herbicide compound, but not in the acid form or not at a pH lower than the pKa of the herbicide compound.
Examples of dosages of herbicide compound for application of a herbicide compound of preferred application compositions of the invention, especially herbicide compositions of the described pH, to a field, can be in the range from about {fraction (1/100)} or {fraction (1/10)} to about 10 pounds herbicide compound per acre, with dosages in the range from about {fraction (1/100)} or {fraction (1/10)} to about 6 pounds herbicide compound per acre being particularly useful, e.g., from about 0.03 to about 0.5 pounds per acre. More resistant plants or different field environments may require higher concentrations and/or higher dosage rates. The preparation of herbicide application compositions suitable to apply useful dosages, based on the concentration of herbicide compound in a MFC or microemulsion will be well understood by those of ordinary skill.
The herbicide compositions can, as indicated, be applied using conventional aerial and field spray techniques in field applications. The herbicide compositions can also be applied by any other useful technique, such as by spot-application to undesired plant growth using a hand-held applicator, or the like.
Advantageously, herbicide compositions of the invention have been found to exhibit the additional advantages of being relatively non-volatile. The advantage of non-volatile herbicide compositions are self-evident to those of skill in the herbicide arts. A non-volatile herbicide composition has the advantage of not evolving, or evolving to a reduced degree, through the air, to inadvertently contact desired plant growth. In practical effect, this advantageous property allows the herbicide compositions of the invention to be applied to undesired plant growth in greater strength or in closer proximity to desired above-ground plant growth.
The herbicide compositions can be used for both immediate and long-term control of a large variety of vegetation including those usually found in agricultural fields such as bushes, scrub brush, vines, and other weeds.
Illustrative of vegetation that can be controlled by compositions of the invention, depending significantly on the identity of the herbicide compound, include: black mustard (brassica nigra), curly dock (rumex crispus), common groundsel (senecio vulgaris), pineapple weed (matricaria matricarioides), swamp smartweed (kelp) (polygonum coccineum), prickly lettus (lactuca scariola), lance-leaved groundcherry (physalis lanceifolia), annual sowthistle (sonchus oleraceus), london rocket (sisymbrium irio), common fiddleneck (amsinckia intermedia), hairy nightshade (solanum sarrachoides), shepherd""s purse (capsella bursa-pastoris), sunflower (helianthus annus), common knotweed (polygonum aviculare), green amaranth (amaranthus hybridus), mare""s tail (conyza canadensis), henbit (lamium amplexicaule), cocklebur (xanthium strumarium), cheeseweed (malva parviflora), lambsquarters (chenopodium album), puncture vine (tribulus terrestris) common purslane (portulaca oleracea), prostrate spurge (euphorbia supina), telegraph plant (heterotheca grandiflora), carpetweed (mollugo verticillata), yellow starthistle (centaurea solstitialis), milk thistle (silybum marianum), mayweed (anthemis cotula), burning nettle (urtica urens), fathen (atriplex patula), chickweed (stellaria media), scarlet pimpernel (anagallis arvensis) redroot pigweed (amaranthus retroflexus), minnerslettuce (montia perfoliata), turkey mullein (eremocarpus setigerus), nettleleaf goosefoot (chenopodium murale), prostrate pigweed (amaranthus blitoides), silverleaf nightshade (solanum elaeagnifolium), hoary cress (cardaria draba), largeseed dodder (cuscuta indecora), California burclover (medicago polymorpha), horse purslane (trianthema portulacastrum), field bindweed (Iconvolvulus arvensis), Russian knapweed (centaurea repens), flax-leaved fleabane (conyza bonariensis), wild radish (raphanus sativus), tumble pigweed (amaranthus albus), stephanomeria (stephanomeria exigua), wild turnip (brassica campestris), buffalo goard (cucurbita foetidissima), common mullein (verbascum thapsus), dandelion (taraxacum officinale), Spanish thistle (xanthium spinosum), chicory (cichorium intybus), sweet anise (foeniculum vulgare), annual yellow sweetclover (melilotus indica), poison hemlock (conium maculatum), broadleaf filaree (erodium botrys), whitestem filaree (erodium moschatum), redstem filaree (erodium cicutarium), ivyleaf morning-glory (ipomea hederacea), shortpod mustard (brassica geniculata), buckhorn plantain (plantago lacenolata), sticky chickweed (cerastium viscosum), himalaya blackberry (rubus procerus), purslane speedwell (veronica peregrina), Mexican tea (chenopodium ambrosioides), Spanish clover (lotus purshianus), Australian brassbuttons (cotula australis), goldenrod (solidago californica), citron (citrullus lanatus), hedge mustard (sisymbrium orientale), black nightshade (solanum nodiflorum), Chinese thornapple (datura ferox), bristly ox tongue (picris echioides), bull thistle (cirsium vulgare), spiny sowthistle (sonchus asper), Tasmanian goosefoot (chenopodium pumilio), goosefoot (chenopodium botrys), wright groundcherry (physalis acutifolia), tomatillo groundcherry (physalis philadelphica), pretty spurge (euphorbia peplus), bitter apple (cucumis myriocarpus), indian tobacco (nicotiana bigelovii), common morning-glory (ipomoea purpurea), waterplantain (alisma triviale), smartweed (polygonum lapathifolium), mature sowthistle (sonchus asper), yellow nutsedge (cyperus esculentus), purple nutsedge (cyperus rotundus), lupine (lupinus formosus), and grasses of the family Gramineae such as annual rye grass, blue grass, water grass, barnyard grass, bermuda grass, fescue, mat grass, Johnson grass, and the like.
The ingredients of the herbicide compositions, e.g., the herbicide compound, surfactant, etc., can be selected in view of the type of control desired (i.e., pre-emergent or post-emergent) and the type of vegetation to be controlled according to the known attributes of the herbicide compound. Additionally, the herbicide compositions should be sufficiently chemically stable to assure that the herbicide compound retains its activity for the period of time required to manufacture, store, transport, and apply the herbicide compositions.
As mentioned, other herbicides or herbicide compositions can optionally be added to herbicide compositions of the invention, to provide broad range protection against certain varieties of plants. As a single example, glyphosate acid (N-phosphonomethylglycine acid) can be useful in combination with the herbicide compositions of the invention.
Glyphosate acid can be included in a herbicide composition in any useful amount, especially in a herbicide application composition in an amount of glyphosate that will provide complementary protection to the other herbicide compound of the herbicide composition. Also, the pH of the herbicide composition can preferably be below the pH of glyphosate acid, e.g., below about 2.6, so the glyphosate can exist in the acid form, preferably improving efficacy and avoiding precipitation.
MFCs of the invention can be prepared by any methods that will be understood as useful to dissolve a herbicide compound in acid form, into a surfactant. In general, the herbicide compound in acid form can typically be provided as a solid, but liquid oil soluble acid herbicide compounds are also typically available. An amount of the herbicide compound in acid form can be dissolved into a surfactant by selecting a proper surfactant or combination of surfactants (combinations of two or more surfactants will be referred to collectively herein as xe2x80x9csurfactantxe2x80x9d), each in useful amounts. As stated, exemplary MFCs can include from about 10 to about 40 parts by weight, e.g., from about 20 to about 35 parts by weight herbicide compound in acid form, and from about 60 to about 90, e.g., from about 65 to about 80 parts by weight surfactant. Useful amounts of herbicide compound in acid form and surfactant can of course be outside of these recited ranges, depending on preference, and on factors such as the solubility of the herbicide compound and whether an organic solvent or water is also present. Heat can optionally be used to facilitate dissolution of herbicide compound in surfactant. For example a mixture of herbicide compound and surfactant (with optional organic solvent) may be heated at a temperature, e.g., in the range from about 100F to about 200F, preferably from about 130 to about 150F, to facilitate dissolution of the herbicide compound in the surfactant. Heat may be applied until dissolution occurs. For example heating a 1 Kg lab batch for a period from of from 30 minutes to 2 hours could generally be useful to dissolve a herbicide compound in acid form. It may be longer for a large production batch of 500-1000 Kg. Organic solvent or water may also be added to the mixture to facilitate dissolution, although it can be preferred to avoid the use of organic solvents. Agitation or other techniques may be used to encourage dissolution.
A skilled artisan will be able to determine whether a particular herbicide compound in acid form can be formed into an MFC by combining a herbicide compound in acid form with a single surfactant or a combination of surfactants, with optional heating, organic solvent, and agitation, to determine whether the surfactant is capable of dissolving the particular herbicide compound. A variety of different surfactants can be used, and a significant number of surfactant or surfactant combinations may have to be attempted to find one or a combination of surfactants that will be effective. Other techniques may also be used to facilitate or encourage dissolution, such as adjusting the speed and degree of agitation or by using slightly higher temperatures.
If other ingredients such as antifoaming agents are included in the MFC or microemulsion, such ingredients can be added as necessary, and in amounts and using techniques that will be well understood. If an acidifying agent is added, it can also be added at any stage of preparation of a herbicide composition, e.g., added to the MFC or by simple combining and mixing an acidifying agent into the microemulsion, e.g., by a dealer or by a consumer (farmer) with a tank mix. Likewise, if other herbicides or herbicide compounds are added to a herbicide composition of the invention, e.g., imidazolinone acid active herbicide compounds or glyphosate acid active herbicide compounds, these may be added by any of these or other methods, as will be appreciated, e.g., normally by simple combination mixing, either by a dealer, by a consumer (farmer) with a tank mix, or otherwise. See, for example, Assignee""s copending U.S. Patent Application entitled xe2x80x9cHerbicide Compositions Comprising Imidazolinone Acid, Methods of Preparation, and Methods of Use,xe2x80x9d having Attorney""s docket number UAP0008/US/2, U.S. Ser. No. ______, filed on even date herewith, and incorporated herein by reference.